This invention relates generally to trimmers for lumber and more particularly to an improved feeding and data entry system for a trimmer.
In most lumber mills, one of the last steps in the manufacturing process is grading, trimming and sorting. Typically, when grading and trimming dry lumber, stacks of lumber coming from dry kilns will be disassembled and the pieces transversely conveyed to the grading station. Usually several graders will visually observe each piece of lumber on one or both sides and mark the piece with a trim indication and a grade indication. The marks are most typically made with chalk on the ends passing by the graders which can then be read by the trimmer operator.
The marked boards are then conveyed to a lug loader. The lug loader acts as a stop for the boards that are randomly entering the system. Then the loader will cycle, causing one board at a time to be placed onto a chain that has lugs affixed at a specific spacing. As the board moves with the fixed lug chain, it will pass through a specific area known as the data entry zone. As the board moves through the data entry zone, the trimmer operator must read the grader's chalk marks and input this information into the trimmer and sorting control system. The fixed lug chain is a continuously moving chain and, therefore, the operator has only a limited (based on drive speed of the lug chain) time to make the entry. If the entry is completed while the board is in the data zone, then when the board reaches the trimmer the appropriate saws will cut the board to length. After being cut to length, the board will be sorted (placed with other boards of similar length and quality).
With most automatic trimming and sorting systems, the data entry zone is at a location downstream of the lug loader and, of course, upstream from the trimmer. The lug chain is set at a speed determined by the supposed capability of the trimmer operator to view and then input the data for each board. Both the trim data and grade must be correctly determined and then correctly input, all while the boards travel through the data entry zone at a high rate. The lug loader continuously feeds boards to open lugs on the lug chain and the operator must keep up with the flow past the fixed data entry zone. Inherent in this state-of-the-art feeding and data entry system is pressure on the trimmer operator. With boards moving past at up to one per second, oftentimes a late entry is made with the consequence being that two boards can be mistrimmed and missorted; once a board moves out of the entry zone and data entered, supposedly for it, it will be trimmed and sorted according to the previous set while the next board within the zone will have improper data entered for it. Then the operator must "catch up" and oftentimes makes erroneous entries under the pressure just to catch up.
In present systems, the trimmer operators try to compensate for the inherent problem by looking at boards upstream from those in the data entry zone in order to memorize the grade and trim marks and then attempt to stay ahead by entering correct data when the particular board is in the data entry zone based on the operator's sense of timing. Once the speed of the lug chain is set, for example at sixty lugs per minute, then the lug loader will kick boards from the upstream chain into each set of lugs sequentially on a continuous basis. If the operator fails to make an entry, than at least one board is erroneously handled and if the operator, as previously mentioned, is in a "catch up" mode, the errors can be compounded.
In the past, if an operator came under such pressure that significant cumulation errors were being made, the only alternative was to slow down the lug chain. This alternative is not a desirable one since overall mill production is then lowered. Usually the trimmer operator would be replaced. In short, the trimmer operator has an extremely stressful job, one that is improved significantly by the present invention.
Accordingly, from the foregoing, one object of the invention is to offer a trimmer operator more flexibility in data entry.
Another object is to reduce the number of mistrimmed and missorted boards coming from the trimmer.
Yet a further object is to reduce the mental pressure and fatigue on the operator.
Still a further object is to provide a surge monitoring capacity through a memory means.
These and many additional objects will become more apparent upon reading the detailed description in combination with the drawing.